1. Field of the Invention
The present invention relates to a lighting device for a display device, a display device and a television receiver.
2. Description of the Related Art
A liquid crystal panel, used in a liquid crystal display device such as a liquid crystal TV set, cannot emit light itself, and therefore a backlight device should be additionally provided as an external lamp. The backlight device is arranged on the back of the liquid crystal panel. The backlight device includes a metallic chassis having an opening on the liquid crystal panel side, and further includes a number of cold cathode tubes as lamps arranged in the chassis. Further included are a number of optical members (such as a diffuser plate), which are arranged in the opening of the chassis so that the lights from the cold cathode tubes can be effectively applied to the liquid crystal panel. An example of a backlight device thus including optical members is disclosed in JP-A-2005-202361.
The backlight device disclosed in JP-A-2005-202361 includes optical members such as a diffuser plate, which has a superior heat releasing property. According to this construction, the luminescent efficiency reduction in the cold cathode tubes can be prevented or suppressed due to the heat release. In the conventional backlight devices including the backlight device disclosed in JP-A-2005-202361, the optical members such as a diffuser plate have homogeneous surfaces. That is, the optical members have properties such as transmittivity or reflectivity, uniformly distributed over their surfaces.
The backlight device thus including optical members having homogeneous surfaces is prone to having illumination brightness uniformly distributed over its surface. However, this construction is not suitable for enhancing the front brightness at the central display area of a liquid crystal display device, for example. Particularly, the growing panel size of a liquid crystal display device will result in a growing need for a technique for enhancing the front brightness.